Research On The Design Method Of Optimization For Analog Circuits Based On Genetic Algorithm

As one of the most important embranchment of Evolvable Hardware (EHW),Evolutionary design of circuits has been the hotspot of worldwide research.Logic synthesis tools based on Hardware Describe Language (HDL) can be usedto perform fast reliable synthesis for digital circuit, while as for analog circuit itstill need analog experts to complete the design manually. So the automaticdesign of analog circuit has been the impendent problem to be solved in circuitdesign. While the optimization of analog circuit parameters is the difficultproblem and more practical task at present.Optimizing theory and optimizing algorithm is discussed in this thesis afterstudying the basic theory, key technique and research status in evolving design ofanalog circuit systematically. From circuit composed of resistors and capacitorsto CMOS circuit exploration has been processed in evolving design andparameters optimization of analog circuit through theory and experiment.The Genetic Algorithm (GA) has been analysed deeply and is comparedwith other optimizing algorithm in theory, and GA is introduced as the feasiblemeans to solve the multi-object design in this thesis. It is proved that only byadaptively adjusting the genetic parameters of GA, the convergence problem canbe solved preferably and also the convergence speed can be improved through thesimulation of mathematical function.Through adjusting the parameters and evolving the structures of filtercomposed of passive componets, the validity of optimization of analog circuit byGenetic Algorithm is proved. Through the study of the improvement of structure,the similarity of the classical structure and the evolved structure is introduced.Analyzing the difficulty of evolutionary design of circuits which is brought bythe inherent limitation of the structure adjusting of analog circuit and combiningthe direction of analog circuits development with the difficulty of actual designof analog circuit, the researching way of optimizing the parameters of analogcircuit based on the fixed structure is established.Based on the above research, one operational amplifier is optimized. Aimingat evolving effect of corresponding circuit, the genetic parameters are adjusted adaptively. The method which combines the manual experience of analog circuitwith improved GA reduces the coding length with the help of design experiencewhich restricts the searching space of coding method. Aiming at variety andrestriction of the parameters in CMOS analog Operational Amplifier, differentOp-Amp for different purpose could be optimized in one fixed structureaccording different performance specification. Basing on simulation results ofHspice, the optimization of CMOS analog Operational Amplifier is achieved. Theparameters and the simulation results of the optimized Op-Amp are presented,and the validity and advantage is proved after comparing with other Op-Ampwhich is optimized by other method in industry.As for bandgap reference, according to the different specifications of diverseconditions, the idea which looks on secondary targets as the boundary restrictionsis proposed, and the problem about multi-objective normalization is solved. Thesecondary optimizing method about “coarse adjusting initially, meticulousadjusting successively” is proposed on the condition that improved GeneticAlgorithm is used. The optimizing design about a piecewise nonlinear curvaturecorrected bandgap reference is realized aiming at the temperature coefficient andthe optimized parameters are gived. The simulation results indicate the advantageand validity of the method comparing with other bandgap references which havereached the leading standard of industry.